Get colors for a UIImage using the private StoreKitUI framework

invokeSKUIImageColorAnalyzer.swift

// Forward declaration
class SKUIAnalyzedImageColors: NSObject {}


// convienence extensions for accessing private properties
extension SKUIAnalyzedImageColors {
    func backgroundColor() -> UIColor {
        return self.valueForKey("_backgroundColor") as! UIColor
    }
    
    func textPrimaryColor() -> UIColor {
        return self.valueForKey("_textPrimaryColor") as! UIColor
    }
    
    func textSecondaryColor() -> UIColor {
        return self.valueForKey("_textSecondaryColor") as! UIColor
    }
}

// load the dylib
guard case let libHandle = dlopen("/System/Library/PrivateFrameworks/StoreKitUI.framework/StoreKitUI", RTLD_NOW) where libHandle != nil else {
    
    fatalError("StoreKitUI not found")
}

// make sure the class exists
guard let analyzerClass: AnyClass = NSClassFromString("SKUIImageColorAnalyzer")  else {
    fatalError("SKUIImageColorAnalyzer lookup failed")
}

// look up the selector
let selector: Selector = "analyzeImage:"

guard case let method = class_getClassMethod(analyzerClass, selector) where method != nil else {
    fatalError("failed to look up \(selector)")
}

// recreation of the method's implementation function
typealias Prototype = @convention(c) (AnyClass, Selector, AnyObject) -> AnyObject? // returns an SKUIAnalyzedImageColors object
let opaqueIMP = method_getImplementation(method)
let function = unsafeBitCast(opaqueIMP, Prototype.self)

// get an image
let img = UIImage(named: "flock.jpg")!

// perform the selector on the image
let val = function(analyzerClass, selector, img)

// access the colors
//val?.valueForKey("_backgroundColor")
val?.backgroundColor()
val?.textPrimaryColor()
val?.textSecondaryColor()